1. Field of the Invention
The present invention relates generally to high-pressure fuel supply pumps and their manufacturing methods. More particularly, the invention relates to a welded structure in which two metals, after being fitted at an annular or tubular section, are tightly connected together at the fitting-in portions by welding.
2. Description of the Related Art
JP-A-2005-342782 and JP-A-2004-17048 discloses techniques in which a tubular metal is fitted into a hole of another tubular metal before the two metals are connected together by welding.
According to the above Publications, the two metals are connected together by supplying an electric current while applying pressure to the fitting-in portions.
Meanwhile, there are other known different techniques for realizing a welded structure comprising a cylinder of a high-pressure fuel supply pump and a housing of the pump. That is, International Publication Pamphlet WO2002/055881 proposes a technique that employs fixing with a fastening jig intended to bring both metals into contact with each other and thus form a sealing section. Also, International Publication Pamphlet WO2006/069819 proposes a technique in which, after peripheral surface sealing of the cylinder by press-fitting, an end of the cylinder is fixed to the pump housing by staking. Additionally, JP-A-2005-279778 discloses connecting the two annular or tubular metals by welding the entire contact surface between both metals, at the fitting-in portions thereof, with a laser.